We can talk about triangles by describing (1) how many sides it has congruent (2) its angles.

Three

A triangle with all three sides congruent to each other is called an equilateral triangle.

A triangle with two of its sides congruent to one another is called an isosceles triangle. Click here to inevestigate the triangle shown. What is true about this triangle? Click here for a script to make your own isosceles triangle and here for a blank sketch pad. Test to see if your observations about the above triangle are also true for the isosceles triangles thatyou make?

What would a triangle look like that had only one side congruent. Review what it means for things to be congruent. Is it possible? Why or why not?

What does it look like for a triangle to have no sides congruent? Click here for a blank sketch pad to try and draw a few. These triangles are called scalene. The following is an example:

"That's RIGHT," if the third angle is 90 degrees, a right angle, then the triangle is called a right triangle. In this case, why do the other two angles have to be acute?